Phenotypic and genotypic differences among naturally occurring coxsackie virus B3 variants

Several naturally occurring variants and two prototype Nancy strains of coxsackie virus B3 (CVB3) were studied comparatively for phenotypic and genotypic properties which would differentiate amyocarditic form myocarditic viruses in mice. Amyocarditic variants replicate to lower titres in heart tissues and produce lower viraemias. The genetic relationship of isolates to the prototype was examined by hybridization (74°C, 0.5 M NaCl) of radiolabelled cDNAs (~ 7.5 kb) to Southern blot transfers of restriction fragments from five overlapping cDNA clones of CVB3. All variants hold the 5' nontranslated sequence closely in common. cDNAs of several variants exhibit little or no hybridization with two to five of the six fragments. This molecular technique did not differentiate amyocarditic from myocarditic viruses, but the data show that nature tolerates considerable genotypic changes in the CVB3 genome.